Brain injuries are part of NFL football and the Chargers are no exception.

A total of four concussions in 32 days sidelined three Chargers players in a recent span. Players leading with the helmet weren't the cause of any of the concussions, a reminder that the NFL's recent moves to prevent brain injuries have limits.

Dunlap, concussed twice this season, said he couldn't recall how the first one happened. Fluker said he blacked out and suffered symptoms for the next several days.

"It was miserable," Fluker said. "I don't ever want to have that feeling again. I felt very sluggish for a few days."

Fluker, 6-foot-5 and 339 pounds, said he'd never suffered a concussion until he and guard Jeromey Clary, 6-6 and 320, collided in practice Sept. 19. At the time, Fluker was in the role of a pass-rusher working an end-tackle stunt.

Three days later, playing at Tennessee, the 6-9 Dunlap was finishing off a block when he was hit from behind and propelled into the ground, the top of his helmet striking the turf first.

"All I know is, I had the guy (blocked), and I came to," he said on Oct. 17.

Dunlap, who was concussed in 2011, the third of his four years with the Eagles, said the symptoms that followed made him grateful he'd had only one other concussion.

"Guys who have multiple concussions who have to go through that, I feel terrible for them," he said two weeks ago. "Because you can’t do anything. The lights are too bright; it makes your head hurt. Sound is too loud; makes your head hurt. Stand up too long; it makes you head hurt. So, it sucks. It’s bad.

"But," he said, also on Oct. 17, "I’m back now. I feel good, no more symptoms, no headaches."

The Chargers held out Dunlap for three weeks and two consecutive games. He returned against the Colts and was part of a shutout of sack leader Robert Mathis in San Diego's 19-9 victory in a Monday Night Football contest.

Six days later, he started against the Jaguars and was knocked backward to the ground by a pass-rusher. The Chargers announced he left the game with a concussion. Afterward in the locker room, Dunlap was smiling and talking with teammates. Three days later, in the team's first and only practice of the week, he worked with the offensive line in a light, 30-minute practice and sprinted afterward. He seems on track to play against the Redskins next Sunday.

In the wake of his concussion, Fluker, the rookie, said he experienced dizziness and light sensitivity. As he began to feel better later in the first week after, he lobbied to play, he said, but Chargers staff and his family told him he would have to wait. He sat out the Week Three game, from which Dunlap and starting guard Chad Rhinehart (toe) departed. He returned in Week Four and played all of San Diego's victory over the Cowboys.

Mathews' concussion, seemingly caused by a Raiders linebacker's knee to the helmet in Week Five, came two weeks after Dunlap first went down.

"It’s something that not a lot of people experience – and it’s bad," he said. "It has to do with your brain. I’d rather have something done with my body than my brain because everything else can pretty much be fixed, but it’s your brain."

Mathews came back to play eight days later against the Colts and again the following week, at Jacksonville. In both games, he punished tacklers and rushed for more than 100 yards, a total he'd last reached in December 2011.

In the immediate aftermath of the concussion, Mathews said he "relaxed" his brain and stayed calm. Two days after leaving the Raiders game, he was confident he would be cleared to play against the Colts. Medical tests proved him right.

Mathews said the key to his 102-yard performance against the Colts was "great blocking."

He ran through arm tackles and pulled away from Colts defenders. Sometimes, he slammed into them straight-on.

More than once, he followed the blocks of his two tackles who'd been concussed a month earlier.

The left tackle Dunlap, had lauded Mathews days before the Jacksonville game by saying, without prompting, that getting Mathews 100 yards rushing each game was the line's desire. Against the Jaguars, when Mathews slammed into the end zone for his first rushing touchdown since last year, Fluker, who'd taken over at left tackle, was among the blockers who lifted him up in celebration.

"It’s always in your head about getting hit in the head again," Mathews said. "But you’ve just go to trust your trainers and trust yourself. Really, it’s all about how you feel. If you’re still feeling the effects of the concussion, there’s no way that you should be even stepping out on the field. But if you feel like your normal self with everything, then you take the proper procedures to get cleared.

"I was raring to go – not the day after (the concussion), but the day after that."